1. Field of the Invention
The present invention relates to a magnetic recording method and device employing a magnetic head and a magnetic recording medium, and particularly it relates to a magnetic recording method and magnetic recording device which employ a magnetic recording medium which is capable of high density recording by high magnetic coercive force and has reduced medium noise. The magnetic recording method of the invention is a magnetic recording method which not only reduces medium noise during on-track time, but also reduces the diffusion and height of medium noise during off-track time.
2. Description of the Related Art
The pulse width Pw50 of a waveform reproduced from in-plane magnetic recording media is known to be related to the magnetostatic characteristics of magnetic coercive force Hc, remanance M.sub.r and magnetic layer thickness t of the medium by the following equation: EQU a.varies.(t .times.M.sub.r /Hc).sub.1/2 EQU Pw50=(2(a+d).sup.2 +(a/2).sup.2).sup. 1/2
Here, d represents the magnetic spacing.
Basically, smaller pulse widths are suitable for high recording density media. Thus, a high density recording medium is preferably a medium which has a minimized magnetic layer thickness and produces the maximum magnetic coercive force. When using magnetic resistance (MR) heads and giant magnetic resistance (G-MR) heads, sufficient output can be obtained even with a tBr of 120 G.mu.m or less.
With current CoCr alloy-based magnetic recording media, the magnetic coercive force has been improved by varying the concentration of Cr and by adding Pt, etc. A greater concentration of Cr in the CoCr alloy is associated with a higher degree of magnetic isolation of the magnetic particles, and can also be employed as a means of lowering the noise.
Recent years have seen a greater demand for reduced medium noise in addition to the high magnetic coercive force for producing practical high sensitivity MR heads. Japanese Unexamined Patent Publication No. 7-105525 concentrates on the fact that the medium noise is related to the degree of magnetic interaction between the magnetic particles (.delta.M value), and the degree of magnetic interaction (maximum .delta.M value) demanded for low noise media is defined as 0.3-0.7. However, this prior art is primarily aimed at reducing the noise in the transition region of magnetization and does not deal with improving the off-track characteristics of medium noise.
A study on track edge noise has been reported by B. D. Martin, D. N. Lambeth et al. in IEEE Trans. Mag., 28, 3276 (1992). According to their report, when a bit cell (hard bit cell) with a magnetization oriented opposite to the previous DC-erased direction is recorded on a medium surface subjected to DC erasure, the track edge noise is caused by disordered magnetization patterns generated on the track edge section of the bit cell.
High track recording density and narrow tracks for high track density are both essential to achieve high density magnetic recording media. However, because of the relative increase in the ratio of the track edges as the tracks are narrowed, reduction in track edge noise has become an issue. It is an object of the present invention to provide a magnetic recording system suitable for high density recording which reduces transition noise while also minimizing the diffusion and size of the track edge noise.